Double injection SCR – Bosch’s development for future emission regulations

For OEMs the diesel engine plays an essential role in achieving their CO2 fleet targets and it will continue to do so in the future. The requirements regarding NOx emissions have increased with the introduction of the RDE legislation (Real Driving Emissions) in Europe and the LEVIII-ULEV regulation in den US; complying with these regulations will require further actions to be taken on the engine and the exhaust system. SCR-based exhaust-gas after-treatment with closed-coupled exhaust system layouts and an intelligent temperature management are the methods of choice to support OEMs in achieving the future emission requirements.In BOSCH’s view the double-injection SCR technology represents an efficient, robust and targeted method to achieve this goal. AdBlue® is injected separately by a closecoupled SCR (coated DPF) and a second SCR located away from the engine. Amongst others, this layout offers benefits regarding the thermal de-coupling of the SCR catalysts and an improved, demand-based AdBlue® injection. In addition it simplifies catalyst monitoring (OBD).This paper discusses these benefits of a double-injection system. To this aim theoretical considerations as well as proofs based upon real measurements will be presented.